1. Field of the Invention
The present invention relates to a resin composition incorporating a polyarylene sulfide (hereafter abbreviated as PAS) with an increased glass transition temperature (Tg), as well as a molded product, a heat resistant molded product produced therefrom, and a soldered molded product of such a heat resistant molded product.
2. Description of the Related Art
PAS compounds, of which polyphenylene sulfide (hereafter abbreviated as PPS) is a representative example, have high melting points, exhibit superior properties of flame resistance and chemical resistance, and offer good fluidity during molding, and as a result, they are widely used as an engineering plastic for the injection molding of various electronic components, mechanical components and automobile components. However, PPS has a low Tg value, and loses durability under high temperature conditions exceeding 100xc2x0 C., making it unsuitable for use in hot water equipment components and the like. Furthermore, PPS exhibits insufficient heat resistance for use in fields which require high heat resistance such as the use of lead-free solder with electronic circuit board components.
Various blends of PAS with other polymers such as polycarbonate, polyphenylene oxide, polysulfone, and polyether sulfone have been proposed with the object of improving the heat resistance, the impact resistance and the flame resistance of PAS (Japanese Examined Patent Application, Second Publication No. Sho 53-13468, Japanese Examined Patent Application, Second Publication No. Sho 56-34032, and Japanese Unexamined Patent Application, First Publication No. Sho 59-164360). However, in these methods, the Tg of the PAS within the blended product shows absolutely no improvement from the Tg of unblended PAS.
Blends of PAS with aromatic polyesters are disclosed in Japanese Unexamined Patent Application, First Publication No. Sho. 53-57255 and others. However, in these cases also, although the blends are improved in impact resistance, etc., the Tg of the PAS within the blended product shows absolutely no improvement over the Tg of unblended PAS.
Consequently, a resin composition incorporating PAS, which is able to retain a high degree of strength and rigidity and also maintain a good level of hot water resistance, even under high temperature conditions exceeding 100xc2x0 C., has remained elusive until now.
An object of the present invention is to raise the Tg value of PAS in order to provide a resin composition incorporating PAS and a molded product produced therefrom, which exhibits superior strength and rigidity and good hot water resistance under high temperature conditions exceeding 100xc2x0 C.
Furthermore, another object of the present invention is to provide a heat resistant molded product with even greater heat resistance by heat treating a molded product produced from the above resin composition.
In addition, yet another object of the present invention is to provide a soldered molded product by increasing the solder resistance temperature of the above heat resistant molded product.
As a result of intensive research aimed at resolving the issues outlined above, the inventors of the present invention discovered that by mixing PAS with an aromatic polyester of a specific structure and with a Tg value higher than that of PAS, a composition could be obtained which retained the superior moldability of PAS, and yet exhibited improved levels of Tg and heat resistance, and were thus able to complete the present invention.
In other words, the present invention relates to a resin composition comprising a polyarylene sulfide, and an aromatic polyester represented by a general formula (1) shown below, and with a higher glass transition temperature than the polyarylene sulfide, 
(wherein, Ar represents either an aromatic ring or a heterocyclic ring; R1 to R4 each represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, which may be the same or different, provided that at least one of these groups is an alkyl group of 1 to 8 carbon atoms; Y represents a single bond, a bivalent hydrocarbon group of 1 to 12 carbon atoms which may incorporate a hetero atom, an oxygen atom, a sulfur atom, a nitrogen atom, a linkage group in which hetero atoms are bonded together, or a linkage group comprising bonding between hetero atoms and carbon atoms; and n is an integer representing the number of repeating units), as well as a molded product produced using such a composition.
Furthermore, the present invention also relates to a heat resistant molded product obtained by heat treating a molded product formed from the aforementioned resin composition.
In addition, the present invention also relates to a soldered molded product produced by soldering the aforementioned heat resistant molded product.
First, a description of a resin composition of the present invention will be given.
A resin composition of the present invention incorporates PAS, and the aforementioned aromatic polyester represented by the general formula (1) with a higher Tg value than PAS. The Tg values were determined using a dynamic viscoelasticity measuring device, in the manner described below. Namely, under conditions including a frequency of 1 Hz and a rate of temperature increase of 4xc2x0 C./minute, the temperature at the lowest temperature peak of the tan xcex5 peaks obtained was recorded as the value of Tg (xc2x0 C.) for PAS in the present invention. The values of Tg for both unblended PAS and the PAS within a composition of the present invention were measured in this manner.
The PAS used in the compositions of the present invention is a polymer represented by the structural formula (-Ar-S-)n (wherein Ar represents an arylene group). Examples of the arylene group (-Ar-) include bivalent aromatic residues such as p-phenylene, m-phenylene, o-phenylene, 2,6-naphthalene and 4,4xe2x80x2-biphenylene, or bivalent aromatic residues incorporating at least two 6 carbon membered aromatic rings such as the residues shown below, 
although each of the aforementioned aromatic rings may also comprise substituent groups such as F, Cl, Br or CH3. These polymers may be homopolymers, random copolymers or block copolymers, and may be linear, branched or cross linked. Mixtures of these polymers may also be used.
Of the above polymers, polymers in which the polyphenylene sulfide represented by the general formula (3) shown below accounts for at least 70 ml % of the structural units are preferred, and polymers with at least 90 mol % are even more preferred. 
The other structural units incorporated within the PAS, other than the PPS structural units, may include any of the aforementioned arylene groups.
This type of PAS can be synthesized by (1) a reaction between a halogen substituted aromatic compound and an alkali sulfide (refer to U.S. Pat. No. 2,513,188, Japanese Examined Patent Application, Second Publication No. Sho 44-27671, and Japanese Examined Patent Application, Second Publication No. Sho 45-3368), (2) a condensation reaction of a thiophenol in the presence of an alkali catalyst or a copper salt (refer to U.S. Pat. No. 3,274,165), (3) a condensation reaction between an aromatic compound and sulfur chloride in the presence of a Lewis acid catalyst (refer to Japanese Examined Patent Application, Second Publication No. Sho 46-27255), with the particular synthetic method used being chosen depending on the polymer required.
The aromatic polyester used in the present invention is represented by the general formula (1) shown below, 
(wherein, Ar represents either an aromatic ring or a heterocyclic ring; R1 to R4 each represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, which may be the same or different, provided that at least one of these groups is an alkyl group of 1 to 8 carbon atoms; Y represents a single bond, a bivalent hydrocarbon group of 1 to 12 carbon atoms which may incorporate a hetero atom, an oxygen atom, a sulfur atom, a nitrogen atom, a linkage group in which hetero atoms are bonded together, or a linkage group comprising bonding between hetero atoms and carbon atoms; and n is an integer representing the number of repeating units), and is an aromatic polyester with a higher Tg value than PAS (although hereafter referred to as simply an aromatic polyester).
Such an aromatic polyester is typically produced from an aromatic dicarboxylic acid and an aromatic diol with at least one alkyl group substituent on the aromatic ring, and in order to cause a shift in the Tg value of the PAS within the composition to a higher temperature value, the Tg of the aromatic polyester should preferably be at least 200xc2x0 C., and even more preferably within a range from 230 to 300xc2x0 C.
The aromatic polyester should also preferably have a weight average molecular weight within a range from 10,000 to 1,000,000.
Of the aromatic polyesters which meet the above requirements, the aromatic polyesters in which all of the groups R1 to R4 in the above general formula (1) are methyl groups are particularly preferred.
Suitable examples of the Ar grouping within the above general formula (1) include both aromatic ring structures and heterocyclic ring structures such as a benzene ring, naphthalene ring, 9-oxofluorene ring, anthracene ring, anthraquinone ring, biphenylene group, terphenyl group, quaterphenyl group, azobenzene group, furan ring, thiophene ring, 4H-pyran ring, 4-oxo-4H-pyran ring, dibenzofuran ring, dibenzothiophene ring, xanthene ring, dibenzodioxin ring, phenoxathiine ring, thianthrene ring, pyrrole ring, indole ring, carbazole ring, pyrazole ring, imidazole ring, pyridine ring, quinoline ring, bipyridine ring and a pyrimidine ring.
Suitable examples of the Y grouping in the above general formula (1) include a single bond (generating the general formula (2) shown below), xe2x80x94C(CH3)2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94C6H4xe2x80x94C(CH3)2xe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94S(xe2x95x90O)2xe2x80x94, xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94C(xe2x95x90O)xe2x80x94, and xe2x80x94Oxe2x80x94.
Of the aforementioned aromatic polyesters, those represented by the general formula (2) shown below, with a Tg value higher than PAS, and with a Tg value which is preferably at least 200xc2x0 C., and even more preferably within a range from 230 to 300xc2x0 C., are preferred. 
(wherein, Ar represents either an aromatic ring or a heterocyclic ring; R1 to R4 each represent a hydrogen atom or an alkyl group of 1 to 8 carbon atoms, which may be the same or different, although at least one of these groups must be an alkyl group of 1 to 8 carbon atoms; and n is an integer representing the number of repeating units). Of these preferred aromatic polyesters, those in which all of the groups R1 to R4 in the above general formula (2) are methyl groups are particularly preferred.
In the aforementioned general formula (2), the Ar grouping represents the same groupings as described above for the general formula (1).
Suitable examples of the aromatic dicarboxylic acid component of an aromatic polyester of the present invention include various dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, 9-oxofluorene dicarboxylic acid, anthracene dicarboxylic acid, anthraquinone dicarboxylic acid biphenylene dicarboxylic acid, terphenyldicarboxylic acid, quaterphenyldicarboxylic acid, azobenzene dicarboxylic acid, furan dicarboxylic acid, thiophene dicarboxylic acid, 4H-pyran dicarboxylic acid, 4-oxo-4H-pyran dicarboxylic acid, dibenzofuran dicarboxylic acid, dibenzothiophene dicarboxylic acid, xanthene dicarboxylic acid, dibenzodioxin dicarboxylic acid, phenoxathiine dicarboxylic acid, thianthrene dicarboxylic acid, pyrrole dicarboxylic acid, indole dicarboxylic acid, carbazole dicarboxylic acid, pyrazole dicarboxylic acid, imidazole dicarboxylic acid, pyridine dicarboxylic acid, quinoline dicarboxylic acid, bipyridine dicarboxylic acid and pyrimidine dicarboxylic acid. These dicarboxylic acids also include the various ester derivatives, acid anhydrides and acid halides thereof.
Of the dicarboxylic acids listed above, isophthalic acid and/or terephthalic acid are preferred, and the relative proportions of these dicarboxylic acids, in terms of the aromatic dicarboxylic acid structural units, should preferably be from 5 to 100 mol % of the isophthalic acid component and 95 to 0 mol % of the terephthalic acid component, with values from 60 to 100 mol % for the isophthalic acid component and 40 to 0 mol % for the terephthalic acid component being even more preferred.
Suitable examples of the aromatic diol component of an aromatic polyester of the present invention include various diols with at least two aromatic rings and at least one alkyl group on an aromatic ring. Specific examples include 3,3xe2x80x2,5,5xe2x80x2-tetraalkyl-(1,1xe2x80x2-biphenyl)-4,4xe2x80x2-diols (with the alkyl groups comprising 1 to 8 carbon atoms), 3,3xe2x80x2-dialkyl-(1,1xe2x80x2-biphenyl)-4,4xe2x80x2-diols (with the alkyl groups comprising 1 to 8 carbon atoms), 2,2xe2x80x2-bis(4-hydroxy-3-methylphenyl)propane, 2,2xe2x80x2-bis(4-hydroxy-3-ethylphenyl)propane, xcex1, xcex1xe2x80x2-bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene, bis (4-hydroxy-3-methylphenyl)methane, bis(4-hydroxy-3,5-dimethylphenyl)ether, bis (4-hydroxy-3,5-dimethylphenyl)sulfide, bis(4-hydroxy-3,5-dimethylphenyl)sulfone, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethylazobenzene, and 4,4xe2x80x2-dihydroxy-3,3xe2x80x2,5,5xe2x80x2-tetramethylbenzophenone.
Of the above compounds, 3,3xe2x80x2,5,5xe2x80x2-tetraalkyl-(1,1xe2x80x2-biphenyl)-4,4xe2x80x2-diols (with the alkyl groups comprising 1 to 8 carbon atoms) are preferred, and 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-(1,1xe2x80x2-biphenyl)-4,4xe2x80x2-diol is particularly preferred.
The aromatic polyester of the present invention can be produced using conventionally known polymerization methods. Examples of suitable methods include (1) interfacial polymerization methods in which an aromatic dicarboxylic acid dihalide and an aromatic diol are dissolved in two separate solvents insoluble with each other, and the two liquids are then mixed and stirred in the presence of an alkali and a catalytic quantity of a quaternary ammonium salt to effect a polycondensation, (2) solution polymerization methods in which an aromatic dicarboxylic acid dihalide and an aromatic diol are reacted in an organic solvent in the presence of an alkali compound such as a tertiary amine which acts as a receptor for an acid, and (3) molten polymerization methods in which either an aromatic dicarboxylic acid and an aromatic diester, or an aromatic dicarboxylate diester and an aromatic diol are used as raw materials, and these are subjected to an ester exchange reaction in a molten state, and aromatic polyesters obtained via any of these methods can be used.
A resin composition of the present invention can be produced by mixing the aforementioned PAS and the aromatic polyester using conventional methods.
In a resin composition of the present invention, it occurs only by using an aromatic diol with a substituent group on the aromatic ring as the diol component of the aromatic polyester, that the Tg value of the PAS within the composition can be shifted towards a higher temperature. The mechanism of this Tg shift remains somewhat unclear, although the inventors of the present invention have surmised that when the PAS and the aromatic polyester are combined, a phenomenon occurs to increase the Tg value of the PAS within the composition to a higher value than that of unblended PAS, either as a result of the substituent group on the aromatic polyester increasing the affinity with the PAS and improving the compatibility, or as a result of a reaction between the PAS and the aromatic polyester. It is already known that in the case of polymer alloys formed from two polymers with different Tg values, usually an improvement in compatibility leads to a phenomenon in which the Tg value of the polymer with the lower Tg value in the composition shifts to a higher value. However, the fact that until now no PAS blended compositions comprising another polymer have exhibited this phenomenon, indicates the uniqueness of the results observed by the inventors of this invention.
In a resin composition of the present invention, the relative mixing ratios of the PAS and the aromatic polyester should preferably be from 99.9 to 20 parts by mass of the PAS and from 0.1 to 80 parts by mass of the aromatic polyester, with compositions comprising from 95 to 50 parts by mass of the PAS and from 5 to 50 parts by mass of the aromatic polyester being even more preferred. Compositions in which the proportion of the aromatic polyester falls within the above range are preferred, as the Tg value of the PAS within the composition can be increased even further, and properties such as the fluidity during molding and the heat resistance can also be further improved.
Conventional fibrous or granulated fillers may also be added to a resin composition of the present invention if required.
The amount of such fillers added should preferably be within a range from 3 to 400 parts by mass per 100 parts by mass of the combination of the PAS and the aromatic polyester, and provided the amount of filler is kept within this range, a variety of properties such as strength, rigidity, heat resistance, and dimensional stability can be further improved.
Specific examples of fillers which can be used in the present invention include glass fiber, carbon fiber, glass milled fiber, boron fiber, whiskers of materials such as potassium titanate and zinc oxide, alumina fiber, asbestos, silicon carbide, aramid fiber, ceramic fiber, metal fiber, gypsum fiber, mica, talc, wollastonite, sericite, kaolin, clay, bentonite, alumina silicate, zeolite, and silicates such as pyrophyllite, as well as carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, metal oxides such as alumina, magnesium oxide, silica, zirconia, titania and iron oxide, as well as glass beads, ceramic beads, boron nitride, silicon carbide and calcium phosphate, and these materials may be used singularly, or in combinations of two or more materials.
The above fillers may be either hollow, or treated with the type of silane based or titanium based coupling agents typically used as treatment agents.
Furthermore, a resin composition of the present invention may also comprise a silane compound. Examples of suitable silane compounds include either one, or two or more of aminoalkoxysilanes, epoxyalkoxysilanes, or vinylalkoxysilanes.
Within the aforementioned group of aminoalkoxysilanes, any silane compound with at least one amino group and at least two alkoxy groups within each molecule is effective, and specific examples include xcex3-aminopropyltriethoxysilane, xcex3-aminopropyltrimethoxysilane, N-xcex2-(aminoethyl)-xcex3-aminopropyltriethoxysilane, N-xcex2-(aminoethyl)-xcex3-aminopropyltrimethoxysilane, N-xcex2-(aminoethyl)-xcex3-aminopropylmethyldiethoxysilane, N-xcex2-(aminoethyl)-xcex3-aminopropylmethyldimethoxysilane, N-phenyl-xcex3-aminopropyltriethoxysilane, and N-phenyl-xcex3-aminopropyltrimethoxysilane.
Furthermore, within the aforementioned group of epoxyalkoxysilanes, any silane compound with at least one epoxy group and at least two alkoxy groups within each molecule is effective, and specific examples include xcex3-glycidoxypropyltriethoxysilane, xcex3-glycidoxypropyltrimethoxysilane, and xcex2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.
In addition, within the aforementioned group of vinylalkoxysilanes, any silane compound with at least one vinyl group and at least two alkoxy groups within each molecule is effective, and specific examples include vinyltriethoxysilane, vinyltrimethoxysilane and vinyltris(xcex2-methoxyethoxy)silane.
The blend amount of this type of silane compound which can be used in the present invention is preferably from 0.01 to 5 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the aforementioned combination of the PAS and the aromatic polyester.
Where necessary, other conventional additives may also be included in small amounts in a composition of the present invention, provided the inclusion of such additives does not impair the actions and effects of the composition. Examples of such additives include mold releasing agents, coloring agents, heat resistance stabilizing agents, ultraviolet stabilizers, lubricants, plasticizers, foaming agents, flame retardants, flame retardant auxiliaries, and rustproofing agents.
Furthermore, the various ultraviolet absorption agents, antioxidants and antistatic agents may also be added to a composition of the present invention to improve the weather resistance, the oxidation resistance, and the antistatic properties, provided such addition does not impair the heat resistance of the composition.
Preparation of a resin composition of the present invention can be performed by various conventional methods including methods wherein the raw materials are premixed in a mixer such as a tumbler or a Henschel mixer, subsequently supplied to a typical molten mixing device such as a uniaxial or biaxial extruder, a Banbury mixer, a kneader or a mixing roller, and then mixed together at a temperature of between 200 and 500xc2x0 C. sufficient to melt the mixture, before being converted into pellets, as well as methods in which the PAS and the aromatic polyester are dissolved in a specific solvent and then mixed in a dissolved state.
A resin composition of the present invention exhibits a Tg value for the incorporated PAS which is higher than that for the unblended PAS, and consequently offers superior strength and rigidity in high temperature environments exceeding 100xc2x0 C., and also possesses good hot water resistance, making the composition particularly useful in applications which require good levels of heat resistance.
A resin composition of the present invention can be used in the production of molded products via a variety of conventional molding methods including injection molding, extrusion molding, injection compression molding, compression molding, and blow molding, although of these methods, this type of composition is particularly suited to injection molding.
A description of a molded product of the present invention follows.
A molded product of the present invention is produced using an aforementioned resin composition.
A molded product formed from a resin composition of the present invention can be converted to a heat resistant molded product, with a Tg value which has been raised even further, by subjecting the molded product to heat treatment, and furthermore such treatment also produces an improvement in the solder resistance temperature.
There are no particular restrictions on the conditions for the heat treatment of the molded product, although the heat treatment temperature, in other words the surface temperature of the molded product, should preferably be kept within a range from 5 to 100xc2x0C. below the melting point of the PAS, and even more preferably from 10 to 85xc2x0 C. below the melting point.
The melting point described above refers to the value measured in accordance with JIS K7121 using a differential scanning calorimeter DSC7 manufactured by PerkinElmer Instruments Inc.
The length of the heat treatment varies depending on the heat treatment temperature used, although the heat treatment should preferably be at least one minute. There are no particular restrictions on the upper time limit for the heat treatment, although heat treatments of not higher than 1000 hours are preferred.
Furthermore, there are no particular restrictions on the actual heat treatment method used for treating the molded product, and methods in which the molded product is simply heated for a predetermined time inside a heating device capable of maintaining the surface of the molded product at a predetermined temperature are suitable. There are no particular restrictions on this heating device, and devices such as a heat circulating electric oven are suitable.
A heat resistant molded product produced by heat treatment of a molded product formed from a resin composition of the present invention has sufficient heat resistance to enable soldering to be performed, and can consequently be applied to articles which are soldered to substrates, namely soldered molded products. For example, an article can be produced by soldering the leads protruding from a heat resistant molded product housing a chip such as an IC to a wiring board. In such a case, even under conditions where the surface temperature of the substrate to which the heat resistant molded product is to be soldered exceeds 230xc2x0 C., the soldering can still be performed without the molded product melting or undergoing any deformation.
Furthermore, a heat resistant molded product of the present invention can also be soldered using so-called xe2x80x9clead freexe2x80x9d solders. In other words, even in the case of the soldering conditions required for lead free solder systems such as Snxe2x80x94Ag systems, Snxe2x80x94Bi systems, Snxe2x80x94Cu systems or Snxe2x80x94Zn systems, which are typically several dozen degrees higher than 230xc2x0 C., an article can still be produced by soldering the leads protruding from a heat resistant molded product housing a chip such as an IC to a wiring board, and even though the surface temperature of the soldered substrate can reach temperatures as high as 280xc2x0 C., the soldering can still be performed without the molded product melting or undergoing any deformation.
In this description, the surface temperature of the soldered substrate refers to the actual temperature measured at the surface of the substrate during the soldering step of the surface mounting technology. Furthermore, the substrate refers to a printed wiring board or circuit board used in the surface mounting process.
A soldering process of the present invention can utilize conventional processes, and in a suitable example, a substrate is placed on a heat resistant belt inside a heating oven (reflow oven) used in a surface mounting process, and the belt is then moved in conveyor style to heat the substrate.
Examples of applications which can take advantage of the superior mechanical strength, heat resistance, solvent resistance and electrical properties of a resin composition of the present invention include the fields of electrical and electronic components, and mechanical components, and specific components include connectors, coil bobbins, various sockets, condensers, variable condensers, optical pickups, various terminal boards, plugs, magnetic head bases, pipes for use in vehicles, air intake nozzles, intake manifolds, carburetors, lamp sockets, lamp reflectors, lamp housings and hot water mechanical components.